The present invention relates to poly-crystalline compositions, articles of manufacture and processes for producing same.
Ash in the form of coal ash and of municipal solid waste coal ash is a major environmental problem. Coal ash represents an incombustible residual formed from mineral admixtures of coal upon its burning at heat power-stations. The quantity of ash depends on the coal composition and ranges from 5% to 13% of the fuel total. Industrial developed countries, which are producing considerable quantities of electric power, face the problem of accumulating huge quantities of coal ash waste.
Altogether, 20% of the coal ash is bottom ash heavy and light melting particles wherein 80% is coal ash, which has light, thin-dispersion particles.
In most countries, part of the coal ash is used in cement as a substitute for shale; in concrete as a substitute for cement and sand; in road construction as a filler to bitumen and in bricks as a substitute for clay. In spite of the above, large amount of the coal ash are not exploited.
U.S. Pat. No. 5,521,132 by Talmy et al., teaches a method of manufacturing ceramic materials on the base of ash from coal and solid municipal waste incineration, mixed with sodium tetraborate and a calcium containing material.
U.S. Pat. No. 5,583,079 by Golitz, et al., discloses a method of ceramic products obtained by mixing coal ash, glass and clay wastes.
U.S. Pat. No. 3,966,9122 to Miller et al., teaches a method of manufacturing of soda-lime glass containing coal ash.
U.S. Pat. No. 4,430,108 to Hojaji et al., teaches a method of manufacturing foam glass from diatomaceous and coal ash.
U.S Pat. No. 5,935,885 to Hnat et al., teaches a process for forming glass ceramic tiles.
However, the above mentioned inventions provide glass products, which have similar properties to those that are already exist in the market. Moreover, the high quantity of iron in the coal ash paints the glass materials in a black color, which limit their possible applications.
There is thus, a widely recognized need for cost effective processes and for products comprising of high amount of coal ashes. Moreover, it will be highly advantageous to have high quality glass poly-crystalline products e.g. high impact strength, high compressive strength, high bending strength high hardness, modulus of elasticity, thermal-resistance, high-temperature strength, wear-resistance, absence of porosity, zero water-absorption and gas-impermeability and low thermal conductivity.
In one embodiment, the invention provides a poly-crystalline composition comprising an amount of SiO2, Al2O3, CaO, Fe2O3, TiO2, MgO, Na2O, Li2O, CeO2, ZrO2, K2O, P2O5, Cr2O3, ZnO and MnO2.
In another embodiment, the invention provides a process for producing a poly-crystalline composition comprising the steps of: mixing a coal ash particle with at least one glass forming agent and at least one crystallization catalyst; melting said coal ash particle, the at least one glass forming agent and the at least one crystallization catalyst to form a mixture; and cooling the resulting mixture to ambient temperature so as to form a homogenous, non-porous poly-crystalline product comprising SiO2, Al2O3, CaO, Fe2O3, TiO2, MgO, Na2O, Li2O, CeO2, ZrO2, K2O, P2O5, Cr2O3, ZnO and MnO2.
In another embodiment, the invention provides an article of manufacture comprising SiO2, Al2O3, CaO, Fe2O3, TiO2, MgO, Na2O, Li2O, CeO2, ZrO2, K2O, P2O5, Cr2O3, ZnO and MnO2.
In another embodiment, the invention provides a poly-crystalline product comprising an amount of SiO2, Al2O3, CaO, Fe2O3, TiO2, MgO, Na2O, Li2O, CeO2, ZrO2, K2O, P2O5, Cr2O3, ZnO and MnO2.
In another embodiment, the invention provides a poly-crystalline product that is produced by a process comprising the steps of: a. mixing coal ash particle with at least one glass forming agent and at least one crystallization catalyst; b. melting the coal ash particle, the at least one glass forming agent and the at least one crystallization catalyst to form a mixture; and c. cooling the resulting mixture to ambient temperature to form a homogenous, non-porous microcrystalline composition comprising SiO2, Al2O3, CaO, Fe2O3, TiO2, MgO, Na2O, Li2O, CeO2, ZrO2, K2O, P2O5, Cr2O3, ZnO and MnO2.
This invention provides a poly-crystalline composition, poly-crystalline product and an article of manufacture which further comprising an amount of 35.0-43.0 percent of SiO2, 29.0-36.0 percent of Al2O3, 1.4-4.1 percent of Fe2O3, 16.0-21.0 percent of CaO, 1.3-15.2 percent of TiO2, 0.6-8.9 percent of K2O, 1.4-6.8 percent of P2O5, 0-6.0 percent of Cr2O3, 0-11.2 percent of ZnO, 0-1.5 percent of MnO2, 0-10.0 percent of MgO, 0-10.2 percent of Na2O, 0-5.0 percent of CeO2, 0-5.0 percent of ZrO2 and 0-10.2 percent of Li2O by weight.
In another embodiment the invention provides a poly-crystalline composition, poly-crystalline product and an article of manufacture which further comprising an amount of 35.0-57.0 percent of SiO2, 15.0-36.0 percent of Al2O3, 1.4-10.0 percent of Fe2O3, 15.0-22.0 percent of CaO, 0.6.-15.2 percent of TiO2, 0.3-11.0 percent of K2O, 1.4-6.8 percent of P2O5, 0-6.0 percent of Cr2O3, 0-11.2 percent of ZnO, 0-11.5 percent of MnO2, 0-10.0 percent of MgO, 0-10.2 percent of Na2O, 0-5.0 percent of CeO2, 0-5.0 percent of ZrO2 and 0-10.2 percent of Li2O by weight.
In another embodiment, in step C, the microcrystalline composition further comprising an amount of 35.0-43.0 percent of SiO2, 29.0-36.0 percent of Al2O3, 1.4-4.1 percent of Fe2O3, 16.0-21.0 percent of CaO, 1.3-15.2 percent of TiO2, 0.6-8.9 percent of K2O, 1.4-6.8 percent of P2O5, 0-6.0 percent of Cr2O3, 0-11.2 percent of ZnO, 0-1.5 percent of MnO2, 0-10.0 percent of MgO, 0-10.2 percent of Na2O, 0-5.0 percent of CeO2, 0-5.0 percent of ZrO2 and 0-10.2 percent of Li2O by weight.
In another embodiment, in step C, the microcrystalline composition further comprising an amount of 35.0-57.0 percent of SiO2, 15.0-36.0 percent of Al2O3, 1.4-10.0 percent of Fe2O3, 15.0-22.0 percent of CaO, 0.6-15.2 percent of TiO2, 0.3-11.0 percent of K2O, 1.4-6.8 percent of P2O5, 0-6.0 percent of Cr2O3, 0-11.2 percent of ZnO, 0-11.5 percent of MnO2, 0-10.0 percent of MgO, 0-10.2 percent of Na2O, 0-5.0 percent of CeO2, 0-5.0 percent of ZrO2 and 0-10.2 percent of Li2O by weight.
The present invention provides for obtaining and using coal ash for the production of poly-crystalline compositions or products and in another aspect the invention provides a process for producing same. The invention is particularly applicable to coal ash that contains large amounts of calcium oxide and transition metals such as iron manganese, chromium, titanium and the like.
As used hereinabove the term xe2x80x9cbottom ashxe2x80x9d or xe2x80x9cbottom coal ashxe2x80x9d presents itself more coarse (0.2-10 millimeters) pieces of ash which did not sweep away by smoke gases and accumulate in the bottom part of the fire box.
As used here in the specifications and in the claims section the term xe2x80x9cfly coal ashxe2x80x9d refers to fine solid particles of ash (5-50 xcexcm) that are carried away by draft or by waste gases and then deposited in flues or trapped in filters or precipitation and the like. The coal ash contain organic materials and metal contaminants.
It should be noted that the term of ash or coal ash hereinabove refer to both fly ash and to bottom ash, unless one of them is stated particularly. As is exemplified in Example 6, both fly ash and bottom ash can be used to prepare the composition and articles of the invention.
In one embodiment of the present invention, there is provided a poly-crystalline composition, a poly-crystalline product and an article of manufacture comprising oxides such as SiO2, Al2O3, CaO, Fe2O3, TiO2, K2O, P2O5, Cr2O3, ZnO, MgO, ZrO2 and MnO2.
The poly-crystalline products are poly-crystalline materials obtained from special glass compositions by means of catalysis crystallization and consisting from one to several crystalline mineralogical phases, uniformly distributed in the remaining glass phase. As used here in the specifications and in the claims section the term xe2x80x9ccatalysts for crystallizationxe2x80x9d refer to substances that serve as a nuclei of crystallization, such as without being limited, titanium dioxide, chromium oxide, zinc oxide, cerium dioxide manganese dioxide, and zirconium dioxide. Changing of the starting glass composition, by changing the glass forming agents or the catalyst type and quality, or the heating or cooling parameters results in glass ceramic materials with predetermined mineralogical compositions and chemical, mechanical and thermal properties.
In another embodiment of the present invention there is provided a process for producing a poly-crystalline product. The process comprises the following steps: mixing coal ash particles with at least one glass forming agent and at least one crystallization catalyst, in a mechanical blender or a pneumatic blender; b. heating in furnaces in temperature in the range of 1400xc2x0 C. to 1600xc2x0 C. and melting the mixture of the coal ash particles, the at least one glass forming agent and the at least one crystallization catalyst to form a mixture. This step can be carried out in a bath, pot, open hearth or electric melters; and c. cooling the resulting mixture to ambient temperature to form a homogenous, non-porous poly-crystalline product comprising SiO2, Al2O3, CaO, Fe2O3, TiO2, K2O, P2O5, Cr2O3, ZnO, MgO, Na2O, Li2O, CeO2, ZrO2 and MnO2. It should be noted in this respect that the heating, melting and cooling steps are carried out under methods and by using apparatuses that are known in the art.
The parameters of the heating and cooling are determined by type of manufactured product and are easy to perform by anyone who is skilled in the art. The cooling step can be an immediate step or a gradual step. Further examples are provided in U.S. Pat. No. 5,935,885.
In another embodiment, the at least one glass forming agent can be selected from the following oxides group: Si2, Al2O3, Li2O, MgO, Na2O, CaO and K2O. Thus, different compositions and different amounts of the glass forming agents will provide products with different colors and different textures that contain metallic contaminants. As used here in Me specifications and in the claims section the term xe2x80x9ctexturexe2x80x9d refer to the smoothness, or the evenness or the uniformity or the glossiness of the product which may be with a glossy, silky, or polished surface or roughly, unsmoothly, bristly, unpolished, metallic, wrinkled leather surface or a granulated surface. The colors of the products can be without being limited black, light and dark green, brown, gray, silver and bronze. The color and the texture of the poly-crystalline are effected by factors like the compositions and the ratio of the different glass forming agents, the crystallization catalysts, the heating temperature, the rate of cooling as well as the atmosphere in the furnace.
In another embodiment of the present intention, the crystallization catalysts are selected from the group consisting of TiO2, Cr2O3, ZnO, CeO2, MnO2, ZrO2. The poly-crystalline composition according to the present invention further comprising by weight, 35.0-43.0 percent of SiO2, 29.0-36.0 percent of Al2O3, 1.4-4.1 percent of Fe2O3, 16.0-21.0 percent of CaO, 1.3-15.2 percent of TiO2, 0.6-8.9 percent of K2O, 1.4-6.8 percent of P2O5, 0-6.0 percent of Cr2O3, 0-11.2 percent of ZnO, 0-1.5 percent of MnO2, 0-10.0 percent of MgO, 0-10.2 percent of Na2O, 0-5.0 percent of CeO2, 0-5.0 percent of ZrO2 and 0-10.2 percent of Li2O.
In another embodiment, the poly-crystalline composition further comprising by weight of 35.0-57.0 percent of SiO2, 15.0-36.0 percent of Al2O3, 1.4-10.0 percent of Fe2O3, 15.0-22.0 percent of CaO, 0.6-15.2 percent of TiO2, 0.3-11.0 percent of K2O, 1.4-6.8 percent of P2O5, 0-6.0 percent of Cr2O3, 0-11.2 percent of ZnO, 0-11.5 percent of MnO2, 0-10.0 percent of MgO, 0-10.2 percent of Na2O, 0-5.0 percent of CeO2, 0-5.0 percent of ZrO2 and 0-10.2 percent of Li2O by weight.
In another embodiment of the present invention, the crystallization catalysts are selected from the group consisting of TiO2, Cr2O3, ZnO, CeO2, MnO2, ZrO2. The poly-crystalline composition according to the present invention further comprising by weight, 25.0-50.0 percent of SiO2, 20.0-45.0 percent of Al2O3, 0.3-6 percent of Fe2O3, 10-30.0 percent of CaO, 0.3-24.0 percent of TiO2, 0.2-15 percent of K2O, 0.3-13 percent of P2O5, 0-6 percent of Cr2O3, 0-20 percent of ZnO, 0-6 percent of MnO2, 0-19.0 percent of MgO, 0-19.0 percent of Na2O, 0-9.0 percent of CeO2, 0-9.0 percent of ZrO2 and 0-19.0 percent of Li2O.
The invented utilization of coal ash for obtaining glass-crystalline materials, (glass-ceramics) provides an example for a technical solution, which utilizes considerable quantities of coal ash for obtaining a new class of materials with improved physical and decoration characteristics in comparison to other materials which currently exist in the market.
Different physical characteristics, such as for example, strength, hardness, thermal resistant and wear resistance distinguish the product and the composition of the present invention from other products and compositions that were described before. As is exemplified in the examples section, there is provided an embodiment of changing the product physical characteristics by adding different glass forming agents and by changing the heating and cooling conditions. Thus, it is possible to provide a product which will suit the applications requirements.
In one embodiment, there is provided a non-porous poly-crystalline composition. In another embodiment the porosity index is in the range of 0.3-0.7% and is about 0.5%. Thus, the invention provides compositions and products that have no water absorption are gas impermeable and also have low thermal conductivity.
In another embodiment the density of the poly-crystalline composition is in the range of 2.5*103 to 2.9*103kg/m3.
The product and composition have strong thermal resistance, whereas in one embodiment, the initial temperature of softening is about 1200xc2x0 C.
As used herein in the specification and in the claims section below the term xe2x80x9caboutxe2x80x9d refers to xc2x120%
As is exemplified in the Examples section, the present invention compositions and products, have a similar stochiometric ratio to poly-crystalline structures that exist in nature. These are for example, without being limited, anorthite crystalline, cordierite crystalline, wollastonite crystalline, lithium disilicate crystalline and chromium oxide crystalline.
The described process of production enables to manufacture glass-ceramic facing plates, which are of uniform quality.
Assessment of the products that were produced according to the processes and the starting materials described in the Examples section revealed the following data:
These materials are better than the building ceramic concerning the porosity index (xcx9c0.5%) but much lower than the practically un-porous glass ceramics (porosity  less than 0.02%). Thermal Coefficient of Linear Expansion is changed within relatively narrow limits (80-100)*10xe2x88x9271/xc2x0 C. that corresponds to the building ceramic, whereas for the usual glass ceramics the range of this parameter is wider from 20 to 120*10xe2x88x9271/xc2x0 C.
Careful assessment of the materials microstructure by electron microscope (Holon Academic Institute of Technology, Israel) showed dense glass ceramic structure with crystal dimensions xcx9c1 mkm. Determination of the mineralogical composition the products of Example 1 by X-ray diffraction (The Ministry of National Infrastructures, Geological Survey, Israel ) revealed that the predominant crystalline phase is anorthite whereas the additional crystalline phase is albite.
Thermal Coefficient of Linear Expansion the glass ceramics (assessed by Israeli Institute of Ceramic and Silicates, Ben-Gurion University of Negev, Israel) was found to be up to 52*10xe2x88x9271/xc2x0 C. The glass density was found to be up to 2.72*103 kg/m3; the porosity less 0.02%; bending strength was up to 150 MPa; temperature strength under load was 1100xc2x0 C. Other mechanical characteristics were performed in Holon Academic Institute of Technology, Israel: micro-hardness HV (Vickers) up to 8.2 GPa, wear resistance five times more than the customary building ceramic. Adhesion in the stick on to the concrete (Standard Institute of Israel) was 1.5-4.0 times (in dependence on the glue) more than the standard requirements. Discharge of radon Rn222 was lower than the sensitivity level of the control-measuring instruments (Nahal Soreq Nuclear Center, Israel). The level of radioactive emission of the product (Nahal Soreg Nuclear Center, Ministry of the Environment, Radiation Safety Division, Israel) was 22 fold less than the permissible level. The glass ceramics products were found to be water-resistant and were stable to acids and alkali effects.
The proposed glass ceramics correspond to Thermal Coefficient of Linear Expansion (T.C.L.E) of wolfram (T.C.L.E of wolframe 43*10xe2x88x9271/xc2x0 C. is near to T.C.L.E of glass ceramic. It allows to introduce them in wolfram fast elements needed in cases when usual sticking is not possible or is dangerous.
Thus, the present invention is directed to an efficient process of utilization of coal ash, which result from municipal waste. The resulted products and compositions are of a high quality, nice and interesting appearance and colors, and have superior physical properties such as compressive strength, bending strength, impact strength, low thermal conductivity.
Moreover, the process of the present invention is a low cost process that does not required additional preparation (such as grinding, purification, concentration and the like).
As is exemplified in the Examples Section, the invention provides methods for producing glass ceramics and marble like glasses, which are made from fly coal ash as well as bottom ash from any part of the world. Example 1-6 relates to coal ash obtained from South Africa, whereas Example 7 and 8 relates respectively to coal ash obtained from USA to a mixed coal derived from Australia and Asia.
By practicing the inventive process and products, ready to use products are provided such as, for example without being limited, articles for house construction, granite, ceramic tiles for internal or external walls and for floor lining. Also, the developed products can be widely used in civil- and industry engineering for lining of different chutes, tubes, boxes, trays, bins and trestles in the food, chemical, mining and other industry fastening elements, coatings, high-voltage insulators, hermetic containers for storage of radioactive waste, parts of pumps, heat exchangers, heat resistant parts, corrosion resistant parts, as antiballistic and the rest.
It will be appreciated that the present invention is not limited by what has been described hereinabove and that numerous modifications, all of which fall within the scope of the present invention, exist. For example, while the present invention has been described with respect to the Examples section, which provides the above described compositions, it will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described herein above. It is to be understood that other close compositions and agents comprising other ratios and other components can be effectively employed in the present invention process, products and compositions.